The purpose of this proposal is to determine the role of leukotrienes and other lipoxygenase metabolites of arachidonc acid in human T cell activation and proliferation. Most of the work involves defining precisely what arachidonic acid metabolites are produced by T cells. I and my coworkers recently discovered that exogenous arachidonic acid substantially and in some cases totally inhibits leukotriene B4 (LTB4) production by mitogenstimulated T cells. Since all previously published studies on arachidonic acid metabolism of T cells included the addition of exogenous arachidonic acid to the culture media, this calls into question in generally accepted concept that T cells do not metabolize arachidonic acid in a major way. Our preliminary results show that LTB4 is the major arachidonic acid metabolize of T cells. In this study, I will attempt to characterize all arachidonic acid metabolities of human T cells and T cell lines using high performance liquid chromatography (HPLC) and radioimmunoassays (RIAs). T cells will be stimulated by a variety of compounds including mitogens, antigens, calcium ionophores, interleukin 1 (IL-1) and IL-2. The role of moncyte derived factors in T cell production of LTB4 will also be assessed. I will also continue my preliminary studies on the precise role of endogenous LTB4 in T cell proliferation. Preliminary results described in the proposal strongly suggest that endogenous LTB4 production is a necessary component of T cell proliferation in response to mitogens. LTB4 is necessary for phytohemagglutinin (PHA) induced IL-2 production, but it may also have a role in the response of activated T cells to IL-2. Future studies will examine the precise relationship between LTB4 production, IL-2 production and T cell proliferation in response to different stimuli, including so-called IL-2 independent mitogens. Both human peripheral blood T cells and a variety of human and murine T cell lines will be used in these experiments.